Preventive Conservation

Environment

Maintain an appropriate, stable environment and control light levels to slow the ageing processes that contribute to the deterioration of paintings. A stable environment is also important to minimise the damage to aged, less flexible canvas and to prevent distortion of wooden backing panels.

Ideally the storage and display environment for paintings should have temperatures and relative humidity levels in the ranges 15 -25 °C and 45 - 55 % respectively with maximum fluctuations of 4 °C and 5 % in any 24 hour period.

Most of the common backing materials, such as canvas, wood, parchment, vellum and even bone and ivory will respond to changes in relative humidity. It is important therefore, when deciding where to hang an artwork, to choose a location that is not prone to large variations in temperature and relative humidity. Do not, for example, hang a painting above a fireplace due to the increased temperatures of the brickwork, the resultant lower relative humidity environment and the possibility of smoke damage. Maintain conditions that will neither encourage embrittlement and desiccation nor too much flexibility and/or mould growth. Methods for controlling relative humidity fluctuations are described elsewhere (see the chapter Preventive Conservation: Agents of Decay).

As watercolours and other paints formed using dyes and lakes are the most sensitive to damage by exposure to light, restrict light levels to 50 lux with a maximum UV level of 30 µW/lumen (1500 µW/m²). Oil, tempera and acrylic paintings can tolerate higher light levels up to 200 lux and 75 µW/lumen (15,000 µW/m²).

Never expose paintings to direct daylight. If windows or skylights are present, use curtains or blinds to eliminate daylight. Cover fluorescent lights with UV filters and install individual switches for each aisle or storage area so that only the minimal quantity of light required for work is used. When the area is not in use, switch off all lights with the exception of emergency lighting. Full details of other light control techniques are available elsewhere (see the chapter Preventive Conservation: Agents of Decay).

Frames and Framing

Frames are both functional and decorative elements. They protect the artwork they surround, provide a means of attaching paintings to the wall and enhance the overall aesthetics of the paintings that they house. Frames original to the painting or selected by the artist are often over-painted, removed or discarded, depending on the current fashion of the day. It is recommended that existing frames on paintings be left ‘as is’ until a significance assessment and condition report have been prepared by a conservator.

For paintings that no longer have frames, framing can provide the correct tension for the canvas, enhance exhibition potential, make storage and handling easier and buffer against changes in ambient conditions. A backboard, for example, minimises relative humidity changes for the support and may help to prevent paint from flaking. Although paintings are generally not glazed as it can detract from the artists’ intent, it serves to protect valuable and fragile paintings by buffering against changes in ambient conditions and by preventing the ingress of dust, dirt and insect excrement.

Commonly used glazing materials include glass and acrylic materials such as Perspex™. Although chemically safe, glass is heavy and can shatter and damage a framed work, whereas acrylics are lighter and shatter-resistant. A further advantage of acrylic glazing is the opportunity to use acrylics that filter UV light. Do not allow direct contact between the painted surface and the glazing as this will increase the risk of mould growth and the abrasion of pigments.

The framing and rehousing of paintings has become a specialised field within conservation (‘conservation framing’) with different materials and methods used from those of typical commercial framing operations. Some differences include the:

• use of archival materials;
• use of a backing board to protect the painting from physical damage, dust and changes in environmental conditions;
• fixing of attachment brackets only to the frame and not to the back of the painting;
• use of padding or a spacer in the gap between the painting and frame to provide a buffer;
• use of UV-filtering acrylic glazing; and
• avoidance of direct contact between the glazing and the surface of the painting.

Before proceeding with framing, make sure that you have checked the following points with the framer:

• the depth of the frame, ensuring that there is room for a spacer and for the painting to be safely positioned;
• the method by which the painting is to be fixed within the frame;
• the types of framing materials that will be used; and
• the types of backing boards and glazing materials used for the painting.

To provide additional environmental protection for particularly valuable paintings, conditioned silica gel or Artsorb® sheets can be incorporated into the frame. Do not attempt this type of treatment without professional advice however as there are risks if correct procedures and conditioning of the silica gel are not carried out.

Handling

Avoid contact with the painted surface and the back of the canvas when handling paintings. This will reduce the chance of leaving fingerprints on varnishes or of dislodging fragile surfaces. Although wearing white cotton gloves is generally recommended when handling paintings, powder-free latex or nitrile gloves are equally acceptable, especially where cotton fibres may catch on uneven surfaces or be deposited on soft paint layers. Take care when handling works displaying impasto techniques or similar artworks, as there is the possibility of the gloves catching on the protruding paint. Other handling recommendations include:

• plan all handling activities carefully. If moving a painting for instance, clear all obstacles from the proposed route and make all necessary preparations for the safe, final placement of the painting;
• clean hands, roll up sleeves and remove jewellery to reduce the risk of damaging the paint surface; 
• hold unframed canvases or panels only at the edges;
• handle framed paintings at the sturdiest part of the frame and not the decorative ornamentation. Never hold frames by the top as this weakens the frame which may break apart if the mitres are already weak;
• inspect paintings and frames carefully before moving them as some older, ornate frames may have sections that are loose;
• as long as the frame is in good condition, carry the framed painting with one hand underneath the bottom of the frame and the other on the side, ensuring that the image side of the painting is facing inwards towards your body;
• if the frame is in poor condition, place it on a support and carry the support;
• if the painting is large, ensure that there are at least three people available to move the painting, one on each end and the other to look out for obstacles and to warn pedestrians;
• have padded blocks available so that the painting can be rested off the floor if necessary; and
• if possible, consider transporting large paintings on padded trolleys. Secure the paintings well before moving to a new location.

To reduce vibration and shock from movement, transport paintings in protective crates with foam padding and use a professional art handling and transportation company where necessary. When particularly valuable objects are moved by commercial transport companies, include vibration and shock data loggers with the paintings to monitor handling practices. These loggers will record the date and time of any physical shock or excessive vibration to which the painting may have been subjected while in transit or storage.

Storage and Display

Before hanging a painting for display, check the frame and hanging system to ensure they are in good order, are sufficient for the weight of the painting and are arranged so the weight is evenly distributed. If there is no hanging system in place, do not simply hammer in nails or use string or cord to hang paintings. Take the painting to a conservation framer for advice on the most appropriate hanging method.

A storage space for paintings should be flexible and take into account the nature of the collection, potential collection growth and changes in exhibition and storage policies. There are many different options ranging from metal bins and storage units to wire mesh moving screens.

Hanging storage using wire mesh moving screens is a good way to store paintings (Figure 4). Wire mesh screens, usually composed of a rigid wire mesh supported on a metal or wooden frame, provide an economic use of floor space and paintings can be easily located and examined in situ. Paintings can be hung (using an appropriate hanging system) on both sides of the screens. These are attached to an overhead and floor track that allow them to be moved manually. Two or more people are normally required to remove paintings from these racking systems.

Figure 4: Wire mesh screen used to store paintings.

Follow the guidelines below if considering the use of wire mesh moving screens to store paintings:

• ensure that the painting is equipped for hanging and is in good condition. Consult a professional framer if it does not have a frame or other form of hanging system;
• consider attaching a backing board to a painting to protect the verso (back) of the painting from damage;
• test the strength of the hanging system and the hooks in the racking before hanging;
• hang heavier paintings lower than lighter paintings;
• check that frames will not damage adjacent frames;
• do not hang paintings in high traffic areas or narrow spaces where they may be accidentally damaged;
• remove or replace wire and hanging hardware that protrudes too far from the back of a painting; and
• do not use vertical storage for paintings that are in poor condition, are fragile or have flaking paint.

If framed images are not hung, store them according to the following guidelines:

• stand paintings upright and in the right orientation;
• place sheets of acid-free board or Fome-cor®, larger than the paintings, between each frame;
• place padding, such as Fome-cor ®, underneath the stack to protect the edges of the frames;
• raise the stack from the floor by using ethafoam blocks, over skidproof mats, or place a wedge against the outermost frame to prevent slippage;
• stack framed works, alternating face-to-face and back-to-back. This prevents the fittings on the back of the frame from scratching the front. Where possible, use pieces of board or other suitable material in between each frame;
• when stacking uneven sized framed works, ‘bridge’ the works so that the frames rest on each other and do not make contact with the painting itself; and
• do not lean or stack paintings against exterior walls.

A custom wooden storage unit consisting of a number of bins can be made to accommodate two to three paintings in each section (Figure 5). Seal all wood (exterior grade plywood), preferably with two to three coats of a water-based polyurethane sealer to reduce off-gassing from the wood. Exterior walls should be at least one inch thick with separating dividers placed in grooves at the top and bottom. Raise the base of the unit so that it is at least 15 cm off the ground and pad the bottom of each section with ethafoam. Place units against an interior wall for added structural and environmental stability. If there is more than one painting in a bin slot, separate each one with some board or other appropriate material.

Figure 5: Custom wooden storage unit comprising individual bins for paintings.

Protect unframed paintings, fragile paintings or those with flaking paint by storing them in custom-made boxes. Construct these boxes from archival materials and store them horizontally in enamelled metal cupboards, map drawers or shelves.

Inspect and monitor paintings regularly, particularly if they are in storage.

Do not use inks or sticky labels on the backs of paintings as they may eventually bleed through to the front or cause puckering to the front of the work. Chemical residues from the adhesive on the labels may also migrate to the front of the work. Catastrophic damage can also be caused by spilling inks or other liquids.

Do not use aerosols and spray cleaners near exposed paintings, as the solvent propellants have the potential to cause softening and damage to paint surfaces.